85 lines
1.6 KiB
Go
85 lines
1.6 KiB
Go
// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import "fmt"
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type printer interface {
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print()
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}
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type list []printer
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func (l list) print() {
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if len(l) == 0 {
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fmt.Println("Sorry. Our store is closed. We're waiting for the delivery 🚚.")
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return
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}
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for _, it := range l {
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it.print()
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}
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}
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func (l list) discount(ratio float64) {
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type discounter interface {
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discount(float64)
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}
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for _, it := range l {
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if it, ok := it.(discounter); ok {
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it.discount(ratio)
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}
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}
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}
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//
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// type assertion can pull out the real value behind an interface value.
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//
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// it can also check whether the value convertable to a given type.
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//
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// func (l list) discount(ratio float64) {
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// for _, it := range l {
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// // remember: interface is a type
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// if it, ok := it.(interface{ discount(float64) }); ok {
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// it.discount(ratio)
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// }
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// }
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// }
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//
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// type switch can pull out the real value behind an interface value.
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//
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// func (l list) discount(ratio float64) {
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// for _, it := range l {
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// switch it := it.(type) {
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// case *game:
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// it.discount(ratio)
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// case *puzzle:
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// it.discount(ratio)
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// }
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// }
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// }
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//
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// type switch can find the type behind an interface value.
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//
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// func (l list) discount(ratio float64) {
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// for _, it := range l {
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// switch it.(type) {
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// case *game:
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// fmt.Print("it's a *game! --> ")
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// case *puzzle:
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// fmt.Print("it's a *puzzle! --> ")
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// default:
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// fmt.Print("neither --> ")
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// }
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// it.print()
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// }
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// }
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